Page 208 - CITS - Electronic Mechanic - TT - 2024

ELECTRONICS MECHANIC - CITS

Diagram of the GSM network organization
The BSS handles traffic between the cellphone and the NSS. It consists of two main components: the base
transceiver station (BTS) and the base station controller (BSC). The BTS contains the equipment that communicates
with the mobile phones, largely the radio transmitter receivers and antennas, while the BSC is the intelligence
behind it. The BSC communicates with and controls a group of base transceiver stations.
The NSS portion of the GSM network architecture, often called the core network, tracks the location of callers to
enable the delivery of cellular services. Mobile carriers own the NSS. The NSS has a variety of parts, including
mobile switching center (MSC) and home location register (HLR). These components perform different functions,
such as routing calls and Short Message Service (SMS) and authenticating and storing caller account information
via SIM cards.
Because many GSM network operators have roaming agreements with foreign operators, users can often continue
to use their phones when they travel to other countries. SIM cards that hold home network access configurations
may be switched to those with metered local access, significantly reducing roaming costs, while experiencing no
reductions in service.
CDMA: Code Division Multiple Access
CDMA stands for Code Division Multiple Access. It is a channel access method used by several radio communication
technologies. It is a digital cellular technology and an example of multiple access. It is generally used for mobile
communication.
Multiple access means that several transmitters can send information simultaneously over a single communication
channel. In this system, different CDMA codes are assigned to different users, and the user can access the whole
bandwidth for the entire duration. It optimizes the use of available bandwidth as it transmits over the entire
frequency range and does not limit the user’s frequency range.
Thus, CDMA allows several users to share a band of frequencies without undue interference between the users.
It is used as an access method in many mobile phone standards.
Usage:
It is used in the Global Positioning System (GPS).
It is used by several mobile phone companies (e.g., Qualcomm standard IS-2000, also known as CDMA2000)
W-CDMA is used in UTMS 3G mobile phone standards.
CDMA has been used in Omni TRACS satellite system for transportation.
Categories of CDMA:
Synchronous CDMA (orthogonal codes)
Asynchronous CDMA (pseudorandom codes)
Difference between CDMA and GSM
The major difference between CDMA and GSM are given below.

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CITS : E & H - Electronics Mechanic - Lesson 118 - 126